I was hoping to better understand the Stormwater Treatment Areas and how they store phosphorous.
I understand that some is captured by aquatic plants, including retention in sedimentary build up after the plants die.
I also understand that some is absorbed by the underlying limestone. It is frequently mentioned that this allows "storage for decades."
My question is, what happens after decades? And why decades? I'm guessing, sorta like activated carbon, the limestone reaches a 'carrying capacity.'
Also, do the periphyton areas have defined life spans of effectiveness before requiring further action, also?
I don't have an academic background in this and I haven't been able to find answers to these questions. Just trying to get a high level understanding. Thanks in advance!
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Phosphorus is stored in the peat that accumulates from the decaying plant materials.
While I built the first periphyton STA demo project, I never could get a good answer on how the phosphorus is stored there and if there is a life span for the PSTA's
Phosphorous is stored as organic phosphates in peat, which is acidic. The phosphorus eventually leaches down into the alkaline limestone layer as the peat decays where it becomes bound up as insoluble calcium phosphate compounds. As limestone weathers away over time, some of the phosphates will enter the groundwater. But this takes a very long time. Like the time required for the limestone substrate to weather away.